Introduction: The occurrence of proteinuria after xenotransplantation of gene-edited (GE) pigs to non-human primates (NHP) is relatively common and may have a serious adverse impact on the prognosis of the xenograft. Our team performed six cases of GTKO/βGalNT2KO/hCD55/TM (4GE) pig-to-rhesus monkey kidney xenotransplantation in 2024, during which anti-CD154 antibody treatment was administered. We observed the occurrence of proteinuria and its influence on the levels of anti-CD154 antibodies and antibody-mediated rejection (AMR).
Methods: Six rhesus monkeys with low levels of performed antibodies against donor pigs received kidney transplants from 4GE pigs. The recipient monkeys received induction therapy with anti-thymocyte globulin (ATG), C1-esterase inhibitors and anti-CD20mAb (rituximab) and maintenance therapy with anti-CD154 antibody, tacrolimus, tocilizumab, and low-dose corticosteroids. Monitoring of the monkeys included frequent complete blood counts, serum metabolic panel (including serum creatinine, blood urea nitrogen, serum total protein, and albumin), and tacrolimus levels, with urine protein levels measured at intervals. Serum and urine levels of anti-CD154 antibody and anti-4GE pig IgM/IgG levels and CDC were measured retrospectively.
Results: Six recipients survived for 57(Case 1), 184(Case 2), 61(Case 3), 45(Case 4), > 184 (Case 5), and > 134(Case 6) days. Among them, 5 cases developed moderate to severe proteinuria (500mg/L-8000mg/L) within 15 to 150 days. Except for the case 2 that proteinuria occurred about 5 months, others occurred about 1 month. After the occurrence of proteinuria, the serum creatinine can still remain within the normal level. However, by detecting the concentrations of anti-CD154 antibodies in serum and urine through flow cytometry, it was found that 1) A significant decrease in the concentration of anti-CD154 antibodies occurred with proteinuria simultaneously; 2) A large amount of anti-CD154 antibodies were detected in the urine, which was positively correlated with the loss level of proteinuria. With the loss of anti-CD154 antibodies, the levels of anti-donor pig IgM and IgG antibodies in 3 cases (Case 2,3,4) showed a significant increase. Pathological examination after graft failure revealed that Case 1 rapidly lost its kidney xenografts due to thrombotic microangiopathy (TMA), while three cases showed significant AMR. In addition, all five cases were accompanied by hypoproteinemia, with significant decreases in both albumin and total protein levels occurring simultaneously.
Conclusions: The changes of proteinuria after kidney xenotransplantation occur earlier than those of renal function and are important indicators that must be monitored regularly. Furthermore, the occurrence of proteinuria is associated with a significant loss of therapeutic anti-CD154 monoclonal antibodies. The loss of anti-CD154 antibodies leads to insufficient immunosuppression and the production of new antibodies, thereby accelerating the AMR process.